The mechanism of nanocrystalline structure formation in Ni3Al during severe plastic deformation

The microstructure evolution of the intermetallic compound Ni3Al during sev ere deformation by torsion under high quasi-hydrostatic pressure. which eve ntually results in the formation of a disordered nanocrystalline structure with a high level of internal stresses, was investigated as a function of t he amount of shear strain. At the microstructural level, the crystals were first fragmented by the propagation of twins, then nanosized equiaxed cryst allites with high misorientations were formed. At the macroscopic level, th ere is evidence that the cold-worked structure first formed at the sample s urface and then propagated into the whole volume. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.